The present invention relates to a fuel system having an integrated pressure management system that manages pressure and detects leaks in a fuel system. The present invention also relates to fuel system having an integrated pressure management system that performs a leak diagnostic for the headspace in a fuel tank, a canister that collects volatile fuel vapors from the headspace, a purge valve, and all associated hoses.
In a conventional pressure management system for a vehicle, fuel vapor that escapes from a fuel tank is stored in a canister. If there is a leak in the fuel tank, canister or any other component of the vapor handling system, some fuel vapor could exit through the leak to escape into the atmosphere instead of being stored in the canister. Thus, it is desirable to detect leaks.
In such conventional pressure management systems, excess fuel vapor accumulates immediately after engine shutdown, thereby creating a positive pressure in the fuel vapor management system. Thus, it is desirable to vent, or xe2x80x9cblow-off,xe2x80x9d through the canister, this excess fuel vapor and to facilitate vacuum generation in the fuel vapor management system. Similarly, it is desirable to relieve positive pressure during tank refueling by allowing air to exit the tank at high flow rates. This is commonly referred to as onboard refueling vapor recovery (ORVR).
According to the present invention, a sensor or switch signals that a predetermined pressure exists. In particular, the sensor/switch signals that a predetermined vacuum exists. As it is used herein, xe2x80x9cpressurexe2x80x9d is measured relative to the ambient atmospheric pressure. Thus, positive pressure refers to pressure greater than the ambient atmospheric pressure and negative pressure, or xe2x80x9cvacuum,xe2x80x9d refers to pressure less than the ambient atmospheric pressure.
The present invention is achieved by providing a fuel system for supplying fuel to an internal combustion engine of a vehicle. The fuel system comprises a fuel tank having a headspace; an intake manifold in fluid communication with the headspace; a charcoal canister in fluid communication with the headspace; a purge valve having a first side in fluid communication with the intake manifold and having a second side in fluid communication with charcoal canister and with the headspace; and an integrated pressure management system. The integrated pressure management system includes a housing connected to the charcoal canister and defining an interior chamber; a pressure operable device separating the chamber into a first portion and a second portion, the first portion communicating with the charcoal canister, the second portion communicating with a vent port, the pressure operable device permitting fluid communication between the charcoal canister and the vent port in a first configuration and preventing fluid communication between the charcoal canister and the vent port in a second configuration; and a switch signaling displacement of the pressure operable device in response to negative pressure at a first pressure level in the charcoal canister.
The present invention is also achieved by a fuel system that comprises a leak detector sensing negative pressure at a first pressure level in a headspace of a fuel tank, a charcoal canister, and fluid conduits interconnecting the fuel tank and charcoal canister; and a pressure operable device operatively connected to the leak detector, the pressure operable device relieving negative pressure below the first pressure level and relieving positive pressure above a second pressure level.
The present invention is further achieved by a method of managing pressure in a fuel system. The fuel system includes a fuel tank, a charcoal canister, and fluid conduits interconnecting the fuel tank and charcoal canister. The method comprises providing an integrated assembly including a switch actuated in response to the pressure and a valve actuated to relieve the pressure; and signaling with the switch a negative pressure at a first pressure level.